The term “raising” is used to describe the
process of excavating large holes between different
levels in a mine, without any use of explosive. The
holes, which are usually steeper than 45°, are called
“raises”. Raises are used as ore chutes, supply ways,
travel ways or ventilation shafts. It is also common to
install service lines in raises for the distribution of
power and other media between the different levels in a
mine. Raises are also excavated in civil-engineering
projects such as hydro-electric power schemes and road
or railway tunnels.
Raises can be excavated using either the
Drill-and-Blast Method or the Raise Boring Method.
Usually, the first step in the Raiseboring process is to
drill a pilot hole downwards. |
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Raiseboring Cutters:
Now in classic black. |
When the pilot hole breaks
through into the lower level, the pilot bit is removed
from the drill string. A reamer is then connected to the
drill string. The reamer is rotated and pulled back up
toward the machine. It is the rotary action and pull-up
thrust of the reamer that crushes the rock.
The advantages of the Raise Boring Method are that it is
safer for personnel, because the machine operator does
not have to be in the shaft during boring. Also there is
no exposure to falling rock, no blasting and no fumes.
Speed is another advantage of the Raise Boring Method.
With modern equipment, production rates of 25 to 30
metres per 24-hour day can be achieved in medium hard
rock.
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